1. Field of the Invention
The present invention relates to a shoe sole and, more particularly, to a shock absorber structure for a shoe sole.
2. Description of the Related Art
Shoe soles are required to have shock absorbing performance.
In prior art shoe soles, generally, the grounding shock while walking is absorbed by the loss of energy by compression transformation of a shock absorbing section, such as the midsole. However, the absorption (or loss) of energy by only compression transformation is generally so low that sufficient shock absorption is not achieved, If the midsole is thickened to raise the energy loss, on the other hand, the shoe sole loses its light weight.
Hack U.S. Pat. No. 2,833,057 and Hack et al U.S. Pat. No. 2,930,149 disclose an outer sole provided with corrugations, undulations and projections each having a ground engaging triangular section. However, in this prior art, because these elements are triangular in section, they generate a large bending transformation, while scarcely performing any shearing transformation.
FIG. 15 herein is a perspective view of the shoe sole disclosed in Yamashita et al U.S. Pat. No. 5,718,063. This prior art discloses a midsole 500 provided with an element 501. However, because the element 501 is integrally formed with the side face of the midsole 500, the midsole 500 performs only a compression transformation as the midsole 500 is compressed. This is because the element 501 is not an element that transforms independently from the compression transformation element.
In Hack, Hack et al., and Yamashita et al., the elements discussed herein are identically formed on both the medial and the lateral sides of the foot. Hence, these elements can not assist in suppressing pronation.
It is, therefore, an object of this invention to improve the shock absorption by redesigning the structure of the shoe sole.
In order to achieve the above-specified object, according to a first aspect of the invention, a shoe sole is provided with a shock absorbing section with a shearing transformation element. This shearing transformation element is supported by a support member at an upper position dislocated forward with respect to a grounding surface so that when a load is applied from above it performs a shearing transformation independently in such a manner as to fall forward.
A second aspect of this invention is directed to a shoe sole having a midsole interposed between an upper suited for enveloping an instep and an outer sole having a treading face on its outer surface. The midsole includes a shearing transformation element. This shearing transformation element has a front end face and a rear end face. The front end face and the rear end face of the shearing transformation element are individually inclined forward as they go upward. With these inclinations of the two end faces, the shearing transformation element performs the shearing transformation in such a manner as to fall forward when a load is applied by the user""s foot at grounding time during walking or running.
When the load W from above is applied by the user""s foot at the grounding time during walking or running, according to this invention, the shearing transformation element falls forward. In effect, the load W creates not only a compression transformation but also a shearing transformation. Generally, the absorption of energy by the shearing transformation is far higher than that by the compression transformation so that even a small shearing transformation can absorb a high amount of energy. This enables a compact structure to exhibit high shock absorption.
There have been proposed in the prior art a number of midsoles having shock absorbing elements formed of extremely thin columns, which perform transformations by falling forward and backward. However, these extremely thin columns perform bending transformations not the shearing transformations of this invention.
In order to perform sufficient shearing transformation, the shearing transformation element is required to have a planar section of a predetermined size. In other words, the shearing transformation element has to be able to perform the required shearing transformation without any substantial bending transformation. For example, in a preferred embodiment, the shearing transformation element has a planar sectional area of preferably 4 cm2 or more and most preferably 6 cm2 or more. Thus, the scope of this invention does not include the prior art thin rod-shaped or plate-shaped elements which are formed into a truss or honeycomb shape.
In the preferred embodiments of the present invention, axes formed of loci of centers of plane sections of said shearing transformation elements are inclined forward as they go upward, respectively. Thereto between the plurality of shearing transformation elements, there are provided soft shock absorbing elements which have a smaller Young""s modulus than that of the shearing transformation elements so that the individual shearing transformation elements can perform shearing transformations without any restriction from each other.
In another preferred embodiment of the present invention, at least the front end face or the rear end face of the shearing transformation element is provided in proximity or contiguity with a soft shock absorbing element. The soft shock absorbing element is set to have a smaller Young""s modulus than that of the shearing transformation element so as to allow the shearing transformation of the shearing transformation element.
Because the shearing transformation element is provided in proximity with the soft shock absorbing element, the shearing transformation element transforms easily to sufficiently perform the shearing transformation function.
A third aspect of this invention is directed to a shoe sole having a midsole interposed between an upper suited for enveloping an instep and an outer sole having a treading face on its outer surface. The midsole comprises: a compression transformation element performing a compression transformation due to a load applied from above; a shearing transformation element performing a shearing transformation in such a manner as to fall forward due to the load applied from above; and a soft shock absorbing element. The shearing transformation element has a hollow portion adapted to enclose the soft shock absorbing element. The soft shock absorbing element is loaded into the hollow portion. The soft shock absorbing element is set to have a smaller Young""s modulus than that of the shearing transformation element so as to allow the shearing transformation of the shearing transformation element.
In this aspect, because the shearing transformation element has the hollow portion, the shearing transformation element can transform easily. Furthermore, because the soft shock absorbing element is loaded into the hollow portion, it does not hold back the transformation of the shearing transformation element, and that is why the shearing transformation element can sufficiently perform the shearing transformation function.
A fourth aspect of this invention is directed to a shoe sole having a midsole interposed between an upper suited for enveloping an instep and an outer sole having a treading face on its outer surface. The midsole comprises: a compression transformation element performing a compression transformation due to a load applied from above; and a shearing transformation element disconnected from the compression transformation element. The shearing transformation element has a front end face and a rear end face. The front end face and the rear end face of the shearing transformation element are individually inclined forward as they go upward. Thereby with these inclinations of the two end faces, the shearing transformation element has a longitudinal section, as taken in the longitudinal direction, formed into a generally parallelogram shape, and the shearing transformation element performs a shearing transformation due to a load at a grounding time of a walking or running user""s foot.
The shearing transformation element of the present aspect transforms independently from the compression transformation element, and has scarcely the continuity of transformation with respect to the compression transformation element. Consequently, satisfactory shearing transformation is exhibited. In addition, the shearing transformation element has a longitudinal section, as taken in the longitudinal direction, formed into a generally parallelogram shape. Consequently, it exhibits satisfactory shearing transformation without performing any bending transformation.
A fifth aspect of this invention is directed to a shoe sole having a midsole interposed between an upper suited for enveloping an instep and an outer sole having a treading face on its outer surface. The midsole comprises: a compression transformation element performing a compression transformation due to a load applied from above; and a shearing transformation element having minimal continuity of transformation relationship to the compression transformation element. The shearing transformation element has a front end face and a rear end face. The front end face and the rear end face of said shearing transformation element are individually inclined forward as they go upward. Thereby with these inclinations of the two end faces, the shearing transformation element performs a shearing transformation due to a load at a grounding time of a walking or running user""s foot, the compression transformation element performs the compression transformation to absorb shock. The shearing transformation element is essentially disposed at a lateral side of a rear foot part in the midsole and is scarcely disposed or not disposed at all at a front foot part and a medial side of the rear foot part in the midsole.
In this aspect the shearing transformation element is disposed at the lateral side of the rear foot part in the midsole. However, the shearing transformation element is not disposed at the medial side of the foot in the midsole. Consequently, at the time of landing on the ground, the lateral side portion of the foot in the midsole performs shearing transformation as well as compression transformation, and absorbs the shock applied to the lateral side of the foot at the time of grounding. On the other hand, since no shearing transformation element is provided on the medial side of the foot, the medial side portion of the foot performs the compression transformation only and does not perform shearing transformation, and that is why it does not greatly transform. As a result, the pronation of the inclining foot toward the medial side is able to be suppressed. That is, in the present invention, even if the lateral side portion of the midsole greatly transforms at the time of grounding, the medial side portion is not easily transformed. Consequently, the pronation is able to be successfully suppressed.
A sixth aspect of this invention is directed to a shoe sole having a midsole interposed between an upper suited for enveloping an instep and an outer sole having a treading face on its outer surface. The midsole has a shearing transformation element, the shearing transformation element performs a shearing transformation due to a load at a grounding time of a walking or running user""s foot.
Either an upper end face or a lower end face of the shearing transformation element is provided in proximity with a soft shock absorbing element which is set to have a smaller Young""s modulus than that of the shearing transformation element.
In this aspect. because the shearing transformation is performed by not only the shearing transformation element but also the soft shock absorbing element, the shearing transformation element can easily perform the shearing transformation. Therefore, shock absorption is improved.